1. Field of the Invention
The present invention relates to ink jet ink, an ink jet recording method, an ink cartridge, and an ink jet recording apparatus.
2. Related Background Art
An ink jet recording method refers to a method which conducts recording of images and texts by allowing fine droplets of ink to fly according various operational principles to apply them on a recording medium (e.g. paper). The technique has features like high speed, low noise, ease in multicolor printing, high flexibility of recording patterns and no need for development and fixing, and is therefore rapidly spreading to a wide variety of applications. In addition, full color ink jet recording system has been recently developed and this enables formation of multi-color images comparable to those by polychromic printing according to a prepress method or printed images produced by color photography. For printing in small numbers, the technique can produce printed matters at lower costs than usual polychromic or photographic printing. Under such circumstances, in response to the demand for improved recording properties including high speed, high definition and full color of recording, improvement of ink jet recording apparatus and recording method has been attempted. Since image forming apparatuses such as printers to which the ink jet recording system is applied are used in various situations, recording stability is also important and in addition, improved durability of images is a property required for ink.
As recording media used in the ink jet recording method, various items such as plain paper, coated paper, glossy paper, OHP sheet and back print film are marketed, while for general use in offices, low price plain paper is mostly used. However, when plain paper is used as a recording medium, it becomes necessary to decrease or prevent curling phenomenon (warping or curl of paper) which occurs when a large amount of ink is applied on the recording medium, while satisfying the aforementioned properties. This curling phenomenon is mainly attributable to applied moisture. That is, it is known that considerable curling phenomenon occurs when moisture is applied to a large area, or in a greater amount. In the case of ink jet recording conducted on plain paper, reduction or suppression of not only curling phenomenon during printing but also curling phenomenon after printing caused by drying and evaporation of moisture (curling phenomenon after printing) have become important.
The printed matter (print) obtained according to the ink jet system are used for various purposes, but curled paper cannot be kept flat, causing a lot of troubles such as curling phenomenon when being piled or put in files. In addition, test printing of presentation documents such as slides and OHP sheet is often conducted on inexpensive plain paper and when figures, photographs or background are printed with the secondary color (blue, etc.), paper becomes warped, making it difficult to handle in many cases.
Some approaches to decrease or prevent curling phenomenon have been proposed so far. For example, ink jet ink containing a solid substance which is soluble in water or an aqueous organic solvent and has four or more hydroxyl groups in a molecular structure is proposed (e.g. see Japanese Patent Application Laid-Open No. H04-332775). In addition, ink containing a saccharide, a sugar alcohol and a specific amide compound as anti-curling agents is proposed (e.g. see Japanese Patent Application Laid-Open No. H06-157955, Japanese Patent Laid-Open No. H06-240189, Japanese Patent Application Laid-Open No. H09-165539 and Japanese Patent Application Laid-Open No. H09-176538). Further, ink containing a specific polyhydric alcohol and glycerol in combination is proposed (see e.g. Japanese Patent Application Laid-Open No. H10-130550). Moreover, ink containing a solvent, a polymer binder, a dye mordant, a water-soluble anti-curling compound, a water-soluble desizing compound, a light resistant compound and a defoaming agent is proposed (e.g. see Japanese Patent Application Laid-Open No. 2000-198267).
Curling phenomenon can be suppressed to some extent by incorporating conventional compounds for preventing curling phenomenon, but ink jet recording has been advanced and involves even higher speed, and ejection stability and reliability are important in the process of high speed printing. Accordingly, in addition to ensuring properties such as stability, permeability and viscosity of the ink itself, it is also important to maintain a high level of basic properties of ink for ink jet recording, in particular, ink jet ejection stability, which is more specifically an anti-clogging property at a ejection port (nozzle) of an ink jet recording head, and a start-up characteristic (re-eject ability of ink from a nozzle after temporal suspension (stopping or pausing) of ink ejection), and at the same time to decrease or prevent curling phenomenon.
Accordingly, an object of the present invention is to provide ink jet ink which can decrease or prevent curling phenomenon with ensuring, as required for conventional ink jet ink, a ejection stability after leaving a head and a ejection stability which can prevent initial portions of printing from being unstable or blurred at the beginning of printing (start-up characteristic), an ink jet recording method, an ink cartridge and an ink jet recording apparatus.
In addition, another object of the present invention is to sufficiently decrease or prevent curling phenomenon, thereby making it easier to handle printed matters prepared by using plain paper.